Character Reference Symbols are used to refer to a single character within a string. This syntax allows you to individually address the characters of a text variable, string variable, or string or text field.

Windows: [[ ]]
MacOS: = = or [[ ]]

On MacOS, you can obtain the ‘=’ and ‘=’ by typing Option + ‘<‘ and Option + ‘>’.
For example, consider this code:

[Contact]Initial:=[Contact]Name[[1]] `Assigns the first character of the name to the Initial field

[Contact]Name[[1]]:=Uppercase([Contact]Name[[1]])